Battery Rundown Protection/Inadvertent Power
WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The BCM inadvertent power supply voltage circuit provides battery positive voltage to all of the interior reading lamps, visor vanity mirror lamps, and the cargo lamps. In the event that any of these lamps were to remain illuminated for a period of more than 10 minutes with the ignition switch in the OFF position, the BCM will deactivate the inadvertent power supply voltage circuit to prevent a total battery discharge condition.
The BCM also utilizes the inadvertent power supply voltage circuit as a lamp request when none of the lamps in the circuit are illuminated. When a lamp switch is activated, the BCM receives the request for lamp illumination and switches to supplying voltage to the inadvertent power supply voltage circuit.